Old English bana "killer, slayer, murderer; the devil," from Proto-Germanic *banon, cognate with *banja- "wound" (source also of Old Frisian bona "murderer," Old Norse bani, Old High German bana "murder," Old English benn "wound," Gothic banja "stroke, wound"), from PIE root *gwhen- "to strike, kill, wound" (source also of Avestan banta "ill"). Modern sense of "that which causes ruin or woe" is from 1570s.